Anxiety problems

Okay so I have really bad social anxiety and sometimes when people I don’t know so well talk to me my mind just starts bouncing off the walls trying to find something to say so I don’t say anything at all. Like today I was helping my boyfriends family out and his grandma told me thank you and said I don’t know what I’d do with your guys help and I couldn’t find any words, I just smiled.

Does anyone think I came off as rude or am I okay? I don’t know what to do when I’m in these situations.